For use in fabricating semiconductor devices or electric elements such as liquid crystals or solar cells, a fabrication apparatus, which performs processing for a processed material, such as a wafer, with the use of high-purity gas of various properties called process gas, is now an indispensable, important industrial machine. The control of these process gases is implemented by opening or closing the valves, which are provided in the downstream side of a mass flow controller via a flow amount controller such as the mass flow controller and are called stop valves or gas valves, according to the step information on the processing recipe.
In the actual processing, the process gas, introduced into the processing chamber or the reaction reactor (chamber), is changed to plasma or is reacted at a high temperature for performing processing such as etching, CVD, ashing, surface modification, or diffusion on a processed material. Because process gas flows into the stop valves and the gas valves, which configure the gas supply system, at a speed of several-cubic cm/minute to several linters/minute and because the valves are opened and closed according to the complex recipe step configuration, durability, reliability, and cleanliness for reducing the adherence of foreign matters onto a processed object are required.
A valve has a cylinder that applies an air pressure of about 0.3 MPa to 0.65 MPa to operate and open the valve. Usually, a normally closed type valve, which is closed when the air supply is stopped to reduce the air pressure in the cylinder, is used. A valve is closed by the pressing force of a spring. A diaphragm or a bellows is used on the contact gas part as a moving part to prevent a leakage of process gas into the external environment. A normally closed type valve, which is closed to stop the gas supply when the electric conduction of the apparatus is turned off for safety, is used in a gas supply system in many cases.
An electromagnetic valve (solenoid valve) is used to supply an air signal for causing these valves to open. The air signal is generated according to the on/off state of the electric signal. On the other hand, there are several types of process gas to be controlled: flammable gas, oxidation gas, poisonous gas, and corrosive gas. For safe use, mixture, and reaction of these gases, various interlock functions are provided on the apparatus to ensure safe processing and working.
As an example in which the interlock function is provided in a circuit that controls the air pressure for controlling valve opening/closing, there is means disclosed in Patent Literature 1.